1. Field of the Invention
The present invention relates to an apparatus for and a method of explosively severing multiple concentric casing strings using explosives.
2. Description of the Prior Art
Once oil or gas wells in inland lakes, bays, tidelands, and offshore waters are abandoned, the owners are required to remove the upper portion of the casing strings to a point below the mudline so they do not present navigational hazards.
The use of explosive charges to cut pipes is known. Early devices and methods utilized for purposes of removing the upper portion of casing strings and also tubular pilings below the mudline relied upon bulk explosives that, after detonation, produced powerful, unfocused explosive charges. Such explosive charges created shock waves that disrupted marine life and the ecosystem surrounding the abandoned well. Further, the charges often "ripped" the casing, but did not completely sever the upper portion, leaving the casing string frayed but not cut, making it difficult to break away the upper portions of the casing.
Other devices and methods for severing pilings and casings strings include loading canister-shaped carriers with explosives positioned at various circumferential locations on the canister. Such devices and methods frequently do not produce an even and complete cut through the piling or casing, and difficulties in focusing the explosive charge are still encountered. If the force of the explosive charge fails to completely sever the piling or casing, a second carrier and charge must be used to complete the severing process. Another apparatus for severing tubular members is disclosed in U.S. Pat. No. 4,787,315, Kenney, Nov. 29, 1988. The apparatus employs deflection plates, which focus the explosive charge. A large amount of explosive must be used, however, particularly if multiple concentric casing strings are to be cut.
Therefore, it is an object of the present invention to provide an apparatus containing an explosive charge wherein detonation produces a focused shock wave that can sever a series of concentric well casing strings using a reduced amount of explosive, and thereby, producing minimal affect on surrounding marine life.
It is a further object of this invention to provide an apparatus for severing multiple strings of casing comprising a container filled with a quantity of a high velocity explosive surrounding a sealed cylinder in the center of the container, a detonator at one end of the container for detonating the high velocity explosive to cause a shock wave and gas bubbles to move toward the center and collapse the cylinder causing it to fail, whereby pressurized air from the cylinder causes the shock wave to move laterally through the casing strings.
It is a further object of this invention to provide a method of simultaneously severing multiple concentric casing strings in an abandoned, oil or gas well located in a body of water comprising lowering an elongated container holding a sealed cylinder in the center of the container and a high velocity explosive surrounding the cylinder, detonating the high velocity explosive so that the high velocity explosive detonates toward the sealed cylinder thereby producing a shock wave and gas bubbles that travel toward the sealed cylinder, the detonating high velocity explosive causing the sealed cylinder to collapse and fail, whereby pressurized air from the cylinder causes the shock wave and gas bubbles from the high velocity explosive to move laterally to sever the upper portions of the concentric casing strings from the lower portions thereof.
It is another object of the present invention to provide a method of simultaneously severing multiple casing strings in an abandoned oil or gas well located in a body of water to allow the upper portion of the casing strings to be removed so as not to be a hazard to navigation, comprising lowering an elongated container holding a mixture of TNT, RDX, and aluminum surrounding a sealed cylinder, detonating the TNT, RDX and aluminum mixture at one end away from the center of the container causing the TNT, RDX, and aluminum mixture to burn toward the sealed cylinder, producing a shock wave and gas bubbles that travel toward the cylinder such that the detonating mixture reaches the cylinder and collapses the cylinder causing it to fail, whereby pressurized air from the cylinder causes the shock wave and gas bubbles from the TNT, RDX, and aluminum mixture to form a concentrated shock wave that moves laterally to sever the casing.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from reading this specification including the attached drawings and appended claims.